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Recent progress in the synthesis of calix[3]pyrrole has proven that cyclic polyketones composed of 3,3-dialkylated pentane-2,4-diones as the repeating unit are promising precursors for strained calix-type macrocycles. Toward the synthesis of calix[2]pyrrole and calix[2]furan, which are the most strained congeners among the possible calix[[Formula: see text]]pyrroles and calix[[Formula: see text]]furans, we report the synthesis of a cyclic dimer of 3,3-dimethylpentane-2,4-dione and its furanophane derivative. These compounds were produced from a linear tetraketone precursor. Single crystal X-ray diffraction analysis revealed that the furan ring in the furanophane was highly strained with deformation angles [Formula: see text] and [Formula: see text] of 3.69[Formula: see text] and 16.00[Formula: see text], respectively. These deformation angles were the largest in the series of 1,4-diketone-linked oligofuran macrocycles. Although these two macrocyclic compounds are likely the most promising precursors for calix[2]-type macrocycles, Paal–Knorr-type pyrrole or furan ring formation did not proceed under standard conditions used for calix[3]pyrrole or calix[3]furan. Theoretical calculations indicated that the second aromatic ring formation on the cyclic tetraketone is a highly uphill process whose activation energy cannot be overcome by standard thermal reactions.

Calix[3]pyrrole and its furan derivatives exhibited bathochromically shifted lowest-energy electronic transition bands in their absorption spectra compared with their calix[4]- and calix[6]-pyrrole analogues, despite the repeating units being the same. We also observed fluorescence emission for calix[3]-type macrocycles. The Stokes shift of the furan/pyrrole hybrid macrocycles, calix[2]furan[1]-pyrrole, and calix[1]furan[2]pyrrole, substantially varied depending on the solvent polarity. Non-covalent interaction (NCI) analyses indicated enhanced interactions between neighboring aromatic rings in the calix[3]pyrrole macrocycle, whereas such interactions were weak in calix[4]pyrrole, in which the interchromophore distance is remarkably longer than in calix[3]pyrrole. Theoretical analyses indicated that the red-shifted, lowest-energy bands of calix[3]pyrrole correspond to HOMO–LUMO transitions, the energy gap of which was narrow compared with calix[4]pyrroles. The characteristic absorption bands for calix[3]pyrrole and its related macrocycles are useful as probes for distinguishing such macrocycles from higher calix[[Formula: see text]]pyrrole ([Formula: see text] 4) analogues that exhibit almost identical absorption spectra.

Cyclic oligoketones composed of 3,3-dimethylpentane-2,4-diones showed crown ether-like alkali metal ion binding behavior with association constants up to 1.7 x 10(4) M-1 in chloroform/acetonitrile (v/v, 9/1). The binding properties have been used for catalysis in the Finkelstein reaction in a low-polarity solvent. Furthermore, novel ion-binding hosts were generated by terminal functionalization of linear polyketones.

Metallo-beta-lactamases (MBLs) are significant threats to humans because they deteriorate many kinds of beta-lactam antibiotics and are key enzymes responsible for multi-drug resistance of bacterial pathogens. As a result of in vitro screening, two compounds were identified as potent inhibitors of two kinds of MBLs: imipenemase (IMP-I) and New Delhi metallo-beta-lactamase (NDM-1). The binding structure of one of the identified compounds was clarified by an X-ray crystal analysis in complex with IMP-1, in which two possible binding poses were observed. Molecular dynamics (MD) simulations were performed by building two calculation models from the respective binding poses. The compound was stably bound to the catalytic site during the simulation in one pose. The binding model between NDM-1 and the compound was constructed for MD simulation. Calculation results for NDM-1 were similar to those of IMP-1. The simulation suggested that the binding of the identified inhibitory compound was also durable in the catalytic site of NDM-1. The compound will be a sound basis for the development of the inhibitors for MBLs.

In this study, we have demonstrated a two-legged, upright molecular design method for monochromatic and bright red luminescent LnIII -silica nanomaterials. A novel EuIII -silica hybrid nanoparticle was developed by using a doubly binding TPPO-Si(OEt)3 (TPPO: triphenyl phosphine oxide) linker. The TPPO-Si(OEt)3 was confirmed by 1 H, 31 P, 29 Si NMR spectroscopy and single-crystal X-ray analysis. Luminescent Eu(hfa)3 and Eu(tfc)3 moieties (hfa: hexafluoroacetylacetonate, tfc: 3-(trifluoromethylhydroxymethylene)camphorate) were fixed onto TPPO-Si(OEt)3 -modified silica nanoparticles, producing Eu(hfa)3 (TPPO-Si)2 -SiO2 and Eu(tfc)3 (TPPO-Si)2 -SiO2 , respectively. Eu(hfa)3 (TPPO-Si)2 -SiO2 exhibited the higher intrinsic luminescence quantum yield (93 %) and longer emission lifetime (0.98 ms), which is much larger than those of previously reported EuIII -based hybrid materials. Eu(tfc)3 (TPPO-Si)2 -SiO2 showed an extra-large intrinsic emission quantum yield (54 %), although the emission quantum yield for the precursor Eu(tfc)3 (TPPO-Si(OEt)3 )2 was found to be 39 %. These results confirmed that the TPPO-Si(OEt)3 linker is a promising candidate for development of EuIII -based luminescent materials.

A long-standing question in porphyrin chemistry is why pyrrole monomers selectively form tetrapyrrolic macrocycles, whereas the corresponding tripyrrolic macrocycles are never observed. Calix[3]pyrrole, a tripyrrolic porphyrinogen-like macrocycle bearing three sp(3)-carbon linkages, is a missing link molecule that might hold the key to this enigma; however, it has remained elusive. Here we report the synthesis and strain-induced transformations of calix[3]pyrrole and its furan analogue, calix[3]furan. These macrocycles are readily accessed from cyclic oligoketones. Crystallographic and theoretical analyses reveal that these three-subunit systems possess the largest strain energy among known calix[n]-type macrocycles. The ring-strain triggers transformation of calix[3]pyrrole into first calix[6]pyrrole and then calix[4]pyrrole under porphyrin cyclization conditions. The present results help explain the absence of naturally occurring three-pyrrole macrocycles and the fact that they are not observed as products or intermediate during classic porphyrin syntheses.

To develop a system in which a pi-conjugation circuit switched by a redox reaction between 3-pyridone and 3-hydroxypyridine, a ring-contracted analog of oxypyriporphyrin, 2-oxypyritriphyrin(1.2.1) was synthesized for the first time. 2-Oxypyritriphyrin(1.2.1) contains a 14 pi aromatic conjugation circuit with the keto-form of the 3-oxypyridine ring. When 2-oxypyritriphyrin was treated with NaBH4, not only the 3-oxypyridine group, but also the meso-carbons were also reduced to give a colorless porphyrinogen analog. The reduced compound could be oxidized again to provide 2-oxypyritripyhrin in a reversible manner.

Critical chain length that divides small molecule crystallization from macromolecular crystallization is an important index in macro-organic chemistry to predict chain-length dependent properties of oligomers and polymers. However, extensive research on crystallization behavior of individual oligomers has been inhibited by difficulties in their synthesis and crystallization. Here, we report on the determination of critical chain length of macromolecular crystallization for structurally flexible polyketones consisting of 3,3-dimethylpentane-2,4-dione. Discrete polyketone oligomers were synthesized via stepwise elongation up to 20-mer. Powder and single crystal X-ray diffraction showed that the critical chain length for polyketones existed at an unexpectedly short chain length, 5-mer. While shorter oligomers adopted unique conformations and packing structures in the solid state, higher oligomers longer than 4-mer produced helical conformations and similar crystal packing. The critical chain length helped with understanding the inexplicable changes in melting point in the shorter chain length region resulting from chain conformations and packing styles.

meso-Carbon extrusion of N-fused [22]pentaphyrin(1.1.1.1.1) occurred upon its PdII complexation, giving N-fused [22]pentaphyrin (1.1.1.1.0) ([22]sapphyrin) PdII complexes 5 and 6 as 22π aromatic compounds. Oxidation of 5 with DDQ and Sc(OTf)3 gave directly C–N linked dimer 7.

One- and two-dimensional coordination polymers composed of a structurally flexible, tetradentate diisopyrazole ligand and copper(I) halides were synthesized as crystalline solids. Complexation with copper(I) chloride or bromide resulted in the formation of infinite coordination chains through connecting each diisopyrazole ligand with two copper(I) ions in a trigonal planar coordination geometry. Contrarily, the combination of a diisopyrazole ligand and copper(I) iodide gave a two-dimensional coordination network comprising Cu4 I4 units with stair-step type geometry and diisopyrazoles that acted as both tetradentate and bidentate bridging ligands. All the coordination polymers exhibited visible photo-emission upon UV irradiation, and the Cu4 I4 complex showed thermochromic behavior.

A dodecahexaene analogue cross-conjugated with four carbonyl groups was prepared from an aliphatic tetraketone. Exposure to LED light (>420 nm) led to the splitting of the dodecahexaene conjugation into two hexatriene subunits, connected through a stereogenic carbon atom. The two triene subunits exhibited excitonic coupling in the UV-Vis absorption and CD spectra.

The recent discovery of calix[3]pyrrole, a porphyrinogen-like tripyrrolic macrocycle, has provided an unprecedented strain-induced ring expansion reaction into calix[6]pyrrole. Here, we synthesized calix[n]furan[3-n]pyrrole (n=1∼3) macrocycles to investigate the reaction scope and mechanism of the ring expansion. Single crystal X-ray analysis and theoretical calculations revealed that macrocyclic ring strain increases as the number of inner NH sites increases. While calix[1]furan[2]pyrrole exhibited almost quantitative conversion into calix[2]furan[4]pyrrole within 5 minutes, less-strained calix[2]furan[1]pyrrole and calix[3]furan were inert. However, N-methylation of calix[2]furan[1]pyrrole induced a ring-expansion reaction that enabled the isolation of a linear reaction intermediate. The mechanism analysis revealed that the ring expansion consists of regioselective ring cleavage and subsequent cyclodimerization. This reaction was further utilized for synthesis of calix[6]-type macrocycles.

We report expanded porphyrins with pyridine rings and two neighboring carbonyl groups, which allow NiII ions to coordinate to the tripyrrinone-type NNNO coordination structure with Ni-O bonds. The selectivity of tripyrrinone is superior to other pyrrolic or pyridinic cavities of expanded porphyrins. Introduction of α-carbonyl pyridine next to the tripyrrolic conjugated structure is a powerful strategy for regioselective metalation of flexible expanded porphyrinoids.

In organometallic complexes containing π-conjugated macrocyclic chelate ligands, conformational change significantly affects metal-ligand electronic interactions, hence tuning properties of the complexes. In this regard, we investigated the metal-ligand interactions in hexaphyrin mono-Pd(II) complexes

In this study, we have demonstrated a two-legged, upright molecular design method for monochromatic and bright red luminescent Ln

Some proteins are easily crystallized by utilizing ammonium sulfate (AS) as a precipitant, while others are not. To investigate the difference of AS behavior in protein crystallization between both...

Structurally flexible oligoisopyrazole molecules were self-assembled into discrete complexes with structural diversity upon palladium coordination. Structural convergence was controlled by a stoichiometry change to induce stepwise metal coordination of isopyrazole subunits. Three different types of complexes were selectively generated from a diisopyrazole ligand. Furthermore, tetraisopyrazole ligands were quantitatively assembled into a discrete complex in a predictable manner.

meso-Carbon extrusion of N-fused [22]pentaphyrin(1.1.1.1.1) occurred upon its Pd

We report aromaticity switching from a 6π pyridine ring to a 22π macrocyclic ring of 3-oxypyripentaphyrin(0.1.1.1.0). This system has potential applications in photodynamic therapy owing to macrocyclic aromaticity being selectively induced by protecting group removal and strong absorption bands produced in the NIR region especially in methanol.

Polyketone compounds play an important role in organic chemistry as a prominent source of reactivity and functionality. Their chemical properties vary widely depending on the ketone sequence in carbon chains. Although vicinal and β-polyketones have been used for more than 150 years, the recent development of new ketone sequences composed of alternating 1,3- and 1,4-diketones has demonstrated the further potential of polyketones as structurally flexible molecular ropes capable of derivatization to π-conjugated chromophores and molecular assemblies. In this Feature Article, we review the synthetic strategies and reactivities of polyketones with respect to their ketone sequence. Furthermore, recent research on polyketones with hybrid ketone sequences is also discussed, focussing on their structural diversity in chemical transformations including intramolecular cyclization and stereoselective oxidation.

Oligoacetylacetones consisting of 3,3-disubstituted pentane-2,4-diones were synthesized through a terminal silylation and oxidative coupling protocol. Highly selective formation of mono-enol silyl ethers of 3,3-disubstituted acetylacetones was achieved using 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) as a base. Subsequent silver(I) oxide mediated coupling reactions provided tetraketones. Unique substituent dependence was found for the terminal-selective silylation of tetraketones. Finally, octaketones (tetramers of acetylacetone derivatives) with three types of monomer sequences were prepared in their discrete forms. Single crystal X-ray analysis revealed that the solid-state conformations of oligoketone chains were predominantly governed by the ketone sequence rather than substituents. However, differences in the packing structures induced by alkyl substituents led to significant differences in melting points for the structural isomers of octaketones.

Conformational control of aliphatic oligoketones bearing two 1,3-diketone subunits is achieved by molecular recognition with pillar[5]arene. Pillar[5]arene binds to aliphatic ketones, with association constants K of ∼10 M-1, to form pseudorotaxanes. The pseudorotaxanes are locked by BF2 complexation at the 1,3-diketone sites through quasi-solid-state reactions. X-ray crystallography reveals linear conformations for the axis molecules. The effect of supramolecular conformational restriction is evaluated using an alkyl-linked dyad chromophore system that shows solvatochromism upon intramolecular aggregation.

Background Species belonging to the genus Aspergillus have been used in traditional Japanese fermented foods. Aspergillus sojae is a species responsible for strong proteolytic activity. Freeze-drying treatments followed by physical disruption enables the pulverization of the mycelia of A. sojae RIB 1045 grown in whey protein-base solid media. Intracellular proteases were extracted using this protocol to compare extracellular protease activity in terms of the reaction's pH dependence in the presence or absence of inhibitors. Result With different sensitivities to inhibitors, intracellular and extracellular proteases showed the strongest activity under acidic conditions, which were considered suitable for cheese application. The raw culture product (CP) and its freeze-dried product (FDP) were mixed with cheese curds, prepared according to Gouda-type cheese-making methods, and were allowed to ripen for 3 months. Chemical analysis of the products showed 13.3% water-soluble nitrogen (WSN) in the control, which had received noncultured media, whereas 20.0% and 21.1% WSN was found in the CP and FDP experimental cheeses, respectively. Although these adjuncts significantly increased WSN, an insignificant difference was found between CP and FDP. Free fatty acids in all experimental cheeses were similar, showing that CP and FDP caused no rancid defects. Conclusion The introduction of freeze-drying treatments accompanied by cell disruption resulted in a negligible effect in terms of WSN. However, the application of A. sojae can be beneficial when it comes to increasing the level of WSN compared with A. oryzae, as shown in our previous study. © 2020 Society of Chemical Industry.

This study revealed S2 fluorescence from deprotonated meso-pentafluorophenyl-substituted Mobius aromatic [32]heptaphyrin(1.1.1.1.1.1.1) that was formed upon treatment of neutral antiaromatic [32]he...

A meso-aryl and β-alkyl substituted sapphyrin and its rhodium(I) and silver complexes were synthesized. This sapphyrin was so stable that the non-inverted and warped structure could be analyzed by X-ray crystallography even in its neutral state. Its bis-rhodium(I) complex has a more planar structure than the sapphyrin with enhanced aromaticity over the conjugation circuit. On the other hand, silver metalation of the sapphyrin caused a marked core rearrangement into a neo-confused sapphyrin derivative with a C(α)-N bond and a twisted macrocycle.

The concise synthesis of symmetric 1,4,5,8-tetraethyl-2,3,6,7-tetravinylporphyrin was developed. The starting material was a close analogue of Knorr's pyrrole prepared from inexpensive commercial β-diketones. The pyrrole was derived into a pair of 3,3′-diacetyl-2,2′-dipyrromethanes. Two precursory dipyrromethanes were coupled to afford tetraacetylporphyrin under the MacDonald condition. The porphyrin was finally converted into a β-tetravinylporphyrin through tetra(1-hydroxyethyl)porphyrin. The structural profile and the utility of the tetravinylporphyrin as the biological prosthetic group and the multiporphyrin scaffold were discussed.

S2 fluorescence from meso-hexakis(pentafluorophenyl)-substituted [26]hexaphyrin dianion was observed as the first example of expanded porphyrins despite its large molecular size and small HOMO–LUMO gap. The population kinetics among S2, S1, and S0 states have been studied by using femtosecond time-resolved absorption and fluorescence spectroscopies. Broad-band fluorescence upconversion spectroscopy allowed for simultaneous observation of S2 fluorescence decay in the visible region and S1 fluorescence rise in the NIR region, both with a time constant of 0.22 ps. The transient absorption spectroscopy revealed the presence of a direct decay path from the S2 state to the S0 state. The observation of S2 fluorescence from highly conjugated molecular systems is quite rare, and S2 fluorescence beyond 700 nm is also quite rare.

Partially β-substituted and meso-tetrakis(pentafluorophenyl)-substituted [22]pentaphyrins 11 and 12 were synthesized by acid-catalyzed condensation of a meso-C6 F5 -substituted tripyrrane dicarbinol with β-alkylated dipyrromethanes. These [22]pentaphyrins are stable, allowing their characterization by NMR and UV/Vis spectroscopies, and X-ray crystallography, and display strong aromaticity due to 22π-electronic circuits. In methanol, β,β-diethoxycarbonylated pentaphyrin 12 underwent an N-fusion reaction to give N-fused pentaphyrin 13, which exhibits crystal polymorphism between Huckel and Mobius structures, depending upon the recrystallization solvent.

Expanded porphyrins with appropriate metalation provide an excellent opportunity to study excited-state aromaticity. The coordinated metal allows the excited-state aromaticity in the triplet state to be detected through the heavy-atom effect, but other metalation effects on the excited-state aromaticity were ambiguous. Herein, the excited-state aromaticity of gold(III) hexaphyrins through the relaxation dynamics was revealed via electronic and vibrational spectroscopy. The SQ states of gold [26]- and [28]-hexaphyrins showed interconvertible absorption and IR spectra with those of counterparts in the ground-state, indicating aromaticity reversal. Furthermore, while the T1 states of gold [28]-hexaphyrins also exhibited reversed aromaticity according to Baird's rule, the ligand-to-metal charge-transfer state of gold [26]-hexaphyrins contributed by the gold metal showed non-aromatic features arising from the odd-number of π-electrons.

Peptidoglycan is an indispensable component of bacterial cell walls. We recently discovered an alternative peptidoglycan biosynthetic pathway, which involves two enzymes, MurD2 and MurL, catalyzing the ligation of L-Glu to UDP-MurNAc-L-Ala and epimerization of the terminal L-Glu of the MurD2 product, respectively. Because the pathway operates in Xanthomonas oryze, a pathogen causing bacterial blight of rice, we searched for specific inhibitors from metabolites produced by actinomycetes to obtain a lead compound to function as an agrochemical. Actinomycin D was isolated from Streptomyces parvulus NBRC 13193 as a specific inhibitor of the pathway. In vitro analysis indicated that actinomycin D inhibited the MurD2 reaction.

The chemo- and stereo-selective two-step transformation of aliphatic polyketones composed of 3,3-dimethylpentane-2,4-dione units was achieved to generate π-conjugated polyimines. Upon treatment with hydrazine, discrete oligoketones with 4-8 carbonyl groups afforded ethylene-bridged oligoisopyrazoles in 80-89% yields. These oligoisopyrazoles underwent stereoselective oxidation at the ethylene bridge to give fully π-conjugated oligo(isopyrazole-3,5-diyl-trans-vinylene)s in 73-87% yields. Oxidation of the oligoimines drastically changed their absorption and metal-coordination behaviors. Finally, this two-step transformation was applied to polydisperse polymers. Imine formation proceeded almost quantitatively, even for longer polyketones, including docosamer. Subsequent oxidation of the polyimines furnished a virtually insoluble material that showed broad and red-shifted solid-state absorption over the whole visible region resulting from extended π-conjugation.

A peripherally strapped [28]hexaphyrin takes a rectangular conformation and exhibits antiaromatic character. A cyclophane-type dimer consisting of such [28]hexaphyrins was synthesized from hexakis(pentafluorophenyl) [26]hexaphyrin via SN Ar reaction with allyl alcohol, one-pot intra- and intermolecular olefin metathesis under improved Hoveyda-Grubbs catalysis, and final reduction with NaBH4 . The cyclophane-type structures of [26]- and [28]hexaphyrin dimers have been revealed by X-ray analysis. Studies on the structural, optical, and electronic properties have led to a conclusion that there is no favorable electronic interaction between the two [28]hexaphyrin segments and thus no indication of 3D aromaticity.

A coiled structure of meso-pentafluorophenyl-substituted [62]tetradecaphyrin 1 was revealed by X-ray structural analysis. Synthetic protocols were devised to form mono- and bis-Zn(II) complexes, 1 Zn and 1 Zn2 , selectively. The former displayed a trigonal-bipyramidal pentacoordinated Zn(II) ion as a rare case and a cyclic voltammogram exhibiting eleven reversible redox waves. The latter showed a Ci-symmetric structure with modest Hückel aromaticity owing to a 62 π-electronic circuit as the largest aromatic molecule to date.

Derivation of the Knorr's pyrrole with 2-ethyl and 4-benzyl mixed-ester groups into 3,3′-diacetyl-5,5′-diiodo-4,4′-dimethyl-2,2′-dipyrromethane was developed. Coupling of the dipyrromethane with 5,5′-diformyl-3,3′-bis(2-methoxycarbonylethyl)-4,4′-dimethyl-2,2′-dipyrro-methane afforded in a reasonable yield diacetyldeuteroporphyin III with C2v symmetry. The porphyrin was further converted to protoporphyrin III through hematoporphyrin III. Utilization of readily available Knorr's pyrrole as the starting material much facilitates the access to symmetric iron porphyrins which are free from the orientational disorder in hemoprotein pocket.

Myoglobin reconstitution with various synthetic heme analogues was reviewed to follow the consequences of modified heme-globin interactions. Utility of dimethyl sulfoxide as the solvent for water-insoluble hemes was emphasized. Proton NMR spectroscopy revealed that loose heme-globin contacts in the heme pocket eventually caused the dynamic heme rotation around the iron-histidine bond. The full rotational rate was estimated to be about 1400 s(-1) at room temperature for 1,4,5,8-tetramethylhemin. The X-ray analysis of the myoglobin containing iron porphine, the smallest heme without any side chains, showed that the original globin fold was well conserved despite the serious disruption of native heme-globin contacts. Comparison between the two myoglobins with static and rotatory prosthetic groups indicated that the oxygen and carbon monoxide binding profiles were almost unaffected by the heme motion. On the other hand, altered tetrapyrrole array of porphyrin dramatically changed the dissociation constant of oxygen from 0.0005 mm Hg of porphycene-myoglobin to ∞ in oxypyriporphyrin-myoglobin. Heme-globin interactions in myoglobin were also monitored with circular dichroism spectroscopy. The observation on several reconstituted protein revealed an unrecognized role of the propionate groups in protoheme. Shortening of heme 6,7-propionates to carboxylates resulted in almost complete disappearance of the positive circular dichroism band in the Soret region. The theoretical analysis suggested that the disappeared circular dichroism band reflected the cancellation effects between different conformers of the carboxyl groups directly attached to heme periphery. The above techniques were proposed to be applicable to other hemoproteins to create new biocatalysts. This article is part of a Special Issue entitled Biodesign for Bioenergetics--the design and engineering of electronic transfer cofactors, proteins and protein networks, edited by Ronald L. Koder and J.L. Ross Anderson.

This study revealed S

Mobius aromatic molecules have attracted great attention as new functional materials because of their π-orbital cyclic conjugations lying along the twisted Mobius topology. To elucidate the electronic character of the lowest excited triplet (T1) state of a Mobius aromatic [28]hexaphyrin, we employed a time-resolved electron paramagnetic resonance (TREPR) method with applied magnetophotoselection measurements at 77 K. Analyses of the EPR parameters have revealed that the T1 state possesses intramolecular charge-transfer (CT) character together with local excitation character residing at one side in the Mobius strip ring. We have also demonstrated that the CT character between orthogonal unpaired orbitals triggers quick triplet deactivation by spin-orbit coupling. This deactivation can be an important barometer to represent the “antiaromaticity” because of a connection between the orthogonal CT character and instability by a weakened spin-spin exchange coupling in the T1 state.

5,10-Bis(pentafluorophenyl)corrole (5) and 5,15-bis(pentafluorophenyl)corrole (9) have been synthesized as meso-free corroles by rational synthetic routes. Both the structures of these corroles have been unambiguously revealed by X-ray diffraction analysis and their optical and electrochemical properties have been studied. Chlorination and oxidative dimerization of 5 and 9 have been explored, which revealed a marked different reactivity of the free meso-positions in 5 and 9. 10-Chlorinated corrole 11 was effectively prepared by the reaction of 9 with Palau'chlor in the presence of 1 % pyridine whereas 5-chlorinated corrole 12 was obtained in a trace amount from similar chlorination of 5. 5,5'-Linked corrole dimer 13 was produced by reaction of 5 with AgNO2 in a good yield, whereas 10,10'-linked corrole dimer 14 was formed in a moderate yield by the reaction of 9 with [bis(trifluoroacetoxy)iodo]benzene. Observed large electronic interaction between the two corroles in 13 as compared with that in 14 has been ascribed mainly to conformational flexibility of the former, which allows more coplanar conformation.

[24]Pentaphyrin(2.1.1.1.1) 1 was synthesized by dehydrogenation of dihydropentaphyrin(2.1.1.1.1) 2 as the first example of vinylogous pentaphyrin. Pentaphyrin 1 takes a roughly planar structure and shows strong antiaromatic character, reflecting a 24π-conjugated circuit. In spite of the antiaromatic character and the relatively small circuit, 1 is stable under ambient conditions.

S

Regioselective nucleophilic chlorination and bromination of [26]hexaphyrin to produce a [28]Möbius aromatic hexaphyrin Pd ( II ) complex were accomplished upon treatment of [26]hexaphyrin 2 with chloride and bromide ions in the presence of an acid with concurrent molecular topology change from Hückel to Möbius. Stille coupling reaction of the resultant 3-brominated complex 4 with ethynylstannanes afforded β-ethynylated derivatives in moderate to high yields.